NPG - recent papers
https://npg.copernicus.org/articles/
Combined list of the recent articles of the journal Nonlinear Processes in Geophysics and the recent discussion forum Nonlinear Processes in Geophysics DiscussionsThe sampling method for optimal precursors of El Niño–Southern Oscillation events
https://doi.org/10.5194/npg-31-165-2024
<b>The sampling method for optimal precursors of El Niño–Southern Oscillation events</b><br>
Bin Shi and Junjie Ma<br>
Nonlin. Processes Geophys., 31, 165–174, https://doi.org/10.5194/npg-31-165-2024, 2024<br>
Different from traditional deterministic optimization algorithms, we implement the sampling method to compute the conditional nonlinear optimal perturbations (CNOPs) in the realistic and predictive coupled ocean–atmosphere model, which reduces the first-order information to the zeroth-order one, avoiding the high-cost computation of the gradient. The numerical performance highlights the importance of stochastic optimization algorithms to compute CNOPs and capture initial optimal precursors.
2024-03-28T13:50:53+01:00Modelling of the terrain effect in magnetotelluric data from the Garhwal Himalaya region
https://doi.org/10.5194/npg-31-175-2024
<b>Modelling of the terrain effect in magnetotelluric data from the Garhwal Himalaya region</b><br>
Suman Saini, Deepak Kumar Tyagi, Sushil Kumar, and Rajeev Sehrawat<br>
Nonlin. Processes Geophys., 31, 175–184, https://doi.org/10.5194/npg-31-175-2024, 2024<br>
This work explores the effect of topography on magnetotelluric (MT) data along a synthetic model of the Roorkee–Gangotri profile (RGP). Two correction procedures were used to remove topography distortion from MT data. Flat-earth and terrain correction responses (TCRs) show that both procedures are capable of removing the topography effect. The similar topographic response and TCRs confirm that there is no need for topography correction along the RGP, as the slope angle is less than 1°.
2024-03-28T13:50:53+01:00Phytoplankton retention mechanisms in estuaries: a case study of the Elbe estuary
https://doi.org/10.5194/npg-31-151-2024
<b>Phytoplankton retention mechanisms in estuaries: a case study of the Elbe estuary</b><br>
Laurin Steidle and Ross Vennell<br>
Nonlin. Processes Geophys., 31, 151–164, https://doi.org/10.5194/npg-31-151-2024, 2024<br>
Phytoplankton are key in estuaries, as they form the ecosystem's base. Despite being washed out by river flow and facing a large range of different salinities, they persist. Our Lagrangian simulation of the Elbe estuary shows that buoyancy helps them to be retained. Riverbanks and tidal flats offer refuges from strong currents. Our findings emphasize the need for careful ecosystem management in estuaries.
2024-03-13T13:50:53+01:00Variational techniques for a one-dimensional energy balance model
https://doi.org/10.5194/npg-31-137-2024
<b>Variational techniques for a one-dimensional energy balance model</b><br>
Gianmarco Del Sarto, Jochen Bröcker, Franco Flandoli, and Tobias Kuna<br>
Nonlin. Processes Geophys., 31, 137–150, https://doi.org/10.5194/npg-31-137-2024, 2024<br>
We consider a one-dimensional model for the Earth's temperature. We give sufficient conditions to admit three asymptotic solutions. We connect the value function (minimum value of an objective function depending on the greenhouse gas (GHG) concentration) to the global mean temperature. Then, we show that the global mean temperature is the derivative of the value function and that it is non-decreasing with respect to GHG concentration.
2024-03-08T13:50:53+01:00Scaling and intermittent properties of oceanic and atmospheric pCO2 time series and their difference
https://doi.org/10.5194/npg-2024-7
<b>Scaling and intermittent properties of oceanic and atmospheric pCO2 time series and their difference</b><br>
Kévin Robache, François G. Schmitt, and Yongxiang Huang<br>
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2024-7,2024<br>
<b>Preprint under review for NPG</b> (discussion: open, 0 comments)<br>
In this work the multi-scale dynamics of 38 oceanic and atmospheric pCO2 time series, sea surface temperature and salinity from fixed buoys recorded with three-hour resolution are considered. The Fourier scaling exponents are estimated. The differences found for 3 ecosystems – coastal shelf, coral reefs, open ocean are discussed. Multifractal properties of pCO2 difference between ocean and atmosphere are found and characterized over the scale range from 3 hours to one year.
2024-03-05T13:50:53+01:00A comparison of two causal methods in the context of climate analyses
https://doi.org/10.5194/npg-31-115-2024
<b>A comparison of two causal methods in the context of climate analyses</b><br>
David Docquier, Giorgia Di Capua, Reik V. Donner, Carlos A. L. Pires, Amélie Simon, and Stéphane Vannitsem<br>
Nonlin. Processes Geophys., 31, 115–136, https://doi.org/10.5194/npg-31-115-2024, 2024<br>
Identifying causes of specific processes is crucial in order to better understand our climate system. Traditionally, correlation analyses have been used to identify cause–effect relationships in climate studies. However, correlation does not imply causation, which justifies the need to use causal methods. We compare two independent causal methods and show that these are superior to classical correlation analyses. We also find some interesting differences between the two methods.
2024-02-27T13:50:53+01:00Extraction of periodic signals in Global Navigation Satellite System (GNSS) vertical coordinate time series using the adaptive ensemble empirical modal decomposition method
https://doi.org/10.5194/npg-31-99-2024
<b>Extraction of periodic signals in Global Navigation Satellite System (GNSS) vertical coordinate time series using the adaptive ensemble empirical modal decomposition method</b><br>
Weiwei Li and Jing Guo<br>
Nonlin. Processes Geophys., 31, 99–113, https://doi.org/10.5194/npg-31-99-2024, 2024<br>
Improper handling of missing data and offsets will affect the accuracy of a signal of interest. The trend in GNSS belonging to GLOSS is key to getting the absolute sea level. However, this is affected by the periodic signals that are included. Although adaptive EEMD is capable of extracting periodic signals, missing data and offsets are ignored in previous work. Meanwhile, the time-varying periodic characteristics derived by adaptive EEMD are more conducive to analyzing the driving factors.
2024-02-21T13:50:53+01:00A two-fold deep-learning strategy to correct and downscale winds over mountains
https://doi.org/10.5194/npg-31-75-2024
<b>A two-fold deep-learning strategy to correct and downscale winds over mountains</b><br>
Louis Le Toumelin, Isabelle Gouttevin, Clovis Galiez, and Nora Helbig<br>
Nonlin. Processes Geophys., 31, 75–97, https://doi.org/10.5194/npg-31-75-2024, 2024<br>
Forecasting wind fields over mountains is of high importance for several applications and particularly for understanding how wind erodes and disperses snow. Forecasters rely on operational wind forecasts over mountains, which are currently only available on kilometric scales. These forecasts can also be affected by errors of diverse origins. Here we introduce a new strategy based on artificial intelligence to correct large-scale wind forecasts in mountains and increase their spatial resolution.
2024-02-13T13:50:53+01:00Part 1: Multifractal analysis of wind turbine power and the associated biases
https://doi.org/10.5194/npg-2024-5
<b>Part 1: Multifractal analysis of wind turbine power and the associated biases</b><br>
Jerry Jose, Auguste Gires, Yelva Roustan, Ernani Schnorenberger, Ioulia Tchiguirinskaia, and Daniel Schertzer<br>
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2024-5,2024<br>
<b>Preprint under review for NPG</b> (discussion: open, 2 comments)<br>
Wind energy exhibits extreme variability in space and time. However, they also show scaling properties (properties that remain similar across different time and space of measurement), this can be quantified using appropriate statistical tools. In this line, the scaling properties of power from a wind farm are analyzed here. Since every turbine is manufactured by design for a rated power, this acts as an upper limit in the data. This bias is identified here using data and numerical simulations.
2024-02-02T13:50:53+01:00Part 2: Joint multifractal analysis of available wind power and rain intensity from an operational wind farm
https://doi.org/10.5194/npg-2024-6
<b>Part 2: Joint multifractal analysis of available wind power and rain intensity from an operational wind farm</b><br>
Jerry Jose, Auguste Gires, Ernani Schnorenberger, Yelva Roustan, Daniel Schertzer, and Ioulia Tchiguirinskaia<br>
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2024-6,2024<br>
<b>Preprint under review for NPG</b> (discussion: open, 2 comments)<br>
To understand the influence of rainfall on wind power production, turbine power and rainfall were simultaneously measured in an operational wind farm and subjected to analysis. The correlation between wind, wind power, air density and other fields was obtained across various temporal scales during rain and dry conditions. An increase in correlation was observed with an increase in rain; rain also influenced the correspondence between actual and expected values of power at various velocities.
2024-02-02T13:50:53+01:00A new approach to understanding fluid mixing in process-study models of stratified fluids
https://doi.org/10.5194/npg-31-61-2024
<b>A new approach to understanding fluid mixing in process-study models of stratified fluids</b><br>
Samuel George Hartharn-Evans, Marek Stastna, and Magda Carr<br>
Nonlin. Processes Geophys., 31, 61–74, https://doi.org/10.5194/npg-31-61-2024, 2024<br>
Across much of the ocean, and the world's lakes, less dense water (either because it is warm or fresh) overlays denser water, forming stratification. The mixing of these layers affects the distribution of heat, nutrients, plankton, sediment, and buoyancy, so it is crucial to understand. We use small-scale numerical experiments to better understand these processes, and here we propose a new analysis tool for understanding mixing within those models, looking at where two variables intersect.
2024-01-30T13:50:53+01:00Leading the Lorenz-63 system toward the prescribed regime by model predictive control coupled with data assimilation
https://doi.org/10.5194/npg-2024-4
<b>Leading the Lorenz-63 system toward the prescribed regime by model predictive control coupled with data assimilation</b><br>
Fumitoshi Kawasaki and Shunji Kotsuki<br>
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2024-4,2024<br>
<b>Preprint under review for NPG</b> (discussion: final response, 2 comments)<br>
Recently, scientists have been looking into ways to control the weather to lead to a desirable direction for mitigating weather-induced disasters caused by torrential rainfall and typhoons. This study proposed using model predictive control, known as an advanced control method, to control a chaotic system. Through numerical experiments using a low-dimensional chaotic system, we demonstrated that the system can be controlled successfully with shorter forecasts compared to previous studies.
2024-01-30T13:50:53+01:00A Comparison of Two Nonlinear Data Assimilation Methods
https://doi.org/10.5194/npg-2024-3
<b>A Comparison of Two Nonlinear Data Assimilation Methods</b><br>
Vivian A. Montiforte, Hans E. Ngodock, and Innocent Souopgui<br>
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2024-3,2024<br>
<b>Preprint under review for NPG</b> (discussion: open, 1 comment)<br>
Advanced data assimilation methods are complex and computationally expensive. We compare two simpler methods, Diffusive Back and Forth Nudging and Concave-Convex Nonlinearity, that account for change over time with the potential of providing accurate results with a reduced computational cost. We evaluate the accuracy of the two methods by implementing them within simple chaotic models. We conclude that the length and frequency of observations impacts which method is better suited for a problem.
2024-01-24T13:50:53+01:00Multifractal structure and Gutenberg-Richter parameter associated with volcanic emissions of high energy in Colima, México (years 2013–2015)
https://doi.org/10.5194/npg-2024-2
<b>Multifractal structure and Gutenberg-Richter parameter associated with volcanic emissions of high energy in Colima, México (years 2013–2015)</b><br>
Marisol Monterrubio-Velasco, Xavier Lana, and Raúl Arámbula-Mendoza<br>
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2024-2,2024<br>
<b>Preprint under review for NPG</b> (discussion: open, 1 comment)<br>
Understanding volcanic activity is crucial for uncovering the fundamental physical mechanisms governing this natural phenomenon. In this study, we show the application of multifractal and statistical analysis, to investigate changes associated with volcanic activity. We aim to identify significant variations within the physical processes related to changes in volcanic activity. These methodologies offer the potential to identify pertinent changes preceding a high-energy explosion.
2024-01-24T13:50:53+01:00Sensitivity of the polar boundary layer to transient phenomena
https://doi.org/10.5194/npg-31-45-2024
<b>Sensitivity of the polar boundary layer to transient phenomena</b><br>
Amandine Kaiser, Nikki Vercauteren, and Sebastian Krumscheid<br>
Nonlin. Processes Geophys., 31, 45–60, https://doi.org/10.5194/npg-31-45-2024, 2024<br>
Current numerical weather prediction models encounter challenges in accurately representing regimes in the stably stratified atmospheric boundary layer (SBL) and the transitions between them. Stochastic modeling approaches are a promising framework to analyze when transient small-scale phenomena can trigger regime transitions. Therefore, we conducted a sensitivity analysis of the SBL to transient phenomena by augmenting a surface energy balance model with meaningful randomizations.
2024-01-19T13:50:53+01:00Aggregation of slightly buoyant microplastics in 3D vortex flows
https://doi.org/10.5194/npg-31-25-2024
<b>Aggregation of slightly buoyant microplastics in 3D vortex flows</b><br>
Irina I. Rypina, Lawrence J. Pratt, and Michael Dotzel<br>
Nonlin. Processes Geophys., 31, 25–44, https://doi.org/10.5194/npg-31-25-2024, 2024<br>
This paper investigates the aggregation of small, spherical, slightly buoyant, rigid particles in a simple 3D vortex flow. Our goal was to gain insights into the behaviour of slightly buoyant marine microplastics in a flow that qualitatively resembles ocean eddies. Attractors are mapped out for the steady, axisymmetric; steady, asymmetric; and nonsteady, asymmetric vortices over a range of flow and particle parameters. Simple theoretical arguments are used to interpret the results.
2024-01-17T13:50:53+01:00Application of Advection-Diffusion Equation for Nonlinearly Evolving Precipitation Field
https://doi.org/10.5194/npg-2023-28
<b>Application of Advection-Diffusion Equation for Nonlinearly Evolving Precipitation Field</b><br>
Ji-Hoon Ha<br>
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2023-28,2024<br>
<b>Preprint under review for NPG</b> (discussion: open, 0 comments)<br>
This study enhances precipitation modeling by addressing the interplay between advection-diffusion effects and source terms. Focused on nonlinearly evolving precipitation, we employed analytic solutions derived through the integral transform technique. Particularly, the field's growth is influenced by source term characteristics (i.e., amplitude, size, timescale) but modulated by advection and diffusion effects. These findings contribute to precipitation-associated water resource management.
2024-01-15T13:50:53+01:00Stability and uncertainty assessment of geoelectrical resistivity model parameters: a new hybrid metaheuristic algorithm and posterior probability density function approach
https://doi.org/10.5194/npg-31-7-2024
<b>Stability and uncertainty assessment of geoelectrical resistivity model parameters: a new hybrid metaheuristic algorithm and posterior probability density function approach</b><br>
Kuldeep Sarkar, Jit V. Tiwari, and Upendra K. Singh<br>
Nonlin. Processes Geophys., 31, 7–24, https://doi.org/10.5194/npg-31-7-2024, 2024<br>
We evaluated three meta-heuristic algorithms using resistivity data. An enormous solution is assessed and the best-fitted solutions are chosen. The posterior probability density function with a 68.27 % confidence interval, a mean and posterior solution, and correlation and covariance matrix were calculated for the assessment of the uncertainty, stability, and mean model. We found that vPSOGWO provides reliable and consistently better results that are correlated well with borehole information.
2024-01-10T13:50:53+01:00Brief Communication: A modified Korteweg–de Vries equation for Rossby–Khantadze waves in a sheared zonal flow of the ionospheric E layer
https://doi.org/10.5194/npg-31-1-2024
<b>Brief Communication: A modified Korteweg–de Vries equation for Rossby–Khantadze waves in a sheared zonal flow of the ionospheric E layer</b><br>
Laila Zafar Kahlon, Hassan Amir Shah, Tamaz David Kaladze, Qura Tul Ain, and Syed Assad Bukhari<br>
Nonlin. Processes Geophys., 31, 1–6, https://doi.org/10.5194/npg-31-1-2024, 2024<br>
It is shown that sheared Rossby–Khantadze waves can propagate due to inhomogeneities, taking into account the Earth's angular velocity and the magnetic field. Along with the Hall conductivity, these waves can couple in the ionospheric E region.The novelty of the present work is the consideration of magnetic field inhomogeneity, which was not considered before and reduced our considered system of equations to a 1D modified KdV equation.
2024-01-09T13:50:53+01:00The dynamic of ion Bernstein-Greene-Kruskal holes in plasmas with regularized κ-distributed electrons
https://doi.org/10.5194/npg-2023-25
<b>The dynamic of ion Bernstein-Greene-Kruskal holes in plasmas with regularized κ-distributed electrons</b><br>
Qiu Ping Lu, Cai Ping Wu, Hui Chen, Xiao Chang Chen, and San Qiu Liu<br>
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2023-25,2024<br>
<b>Preprint under review for NPG</b> (discussion: final response, 3 comments)<br>
As spectral index and cut-off parameter increase, the deeper ion holes are formed and the region where the ion holes exist becomes smaller. On the contrary, the shallower ion holes are formed and the region where the ion holes exist becomes larger when spectral index and cut-off parameter decrease.
2024-01-08T13:50:53+01:00